This invention relates to a technique for measuring the time taken for a machine part, e.g. the blade of a guillotine or a press, to come to a halt, or an approximate halt, after a stopping process has been initiated.
A technique is known in which a sheet bearing a series of lines is fixed to the machine part and viewed by an optical system. The optical system includes a photodetector and movement of the series of lines across the field of view of the system causes the photodetector to produce an output having a characteristic dependent on the velocity of movement. This enables identification of an instant when the machine part comes to a halt or almost to a halt, thus enabling a measure of the braking effectiveness to be made.
A problem associated with the aforementioned technique is to align the optical system with the sheet bearing the series of lines, and to cope with varying ambient light conditions.